An image sensor may be equipped with an anti-eclipse circuit, which prevents and/or corrects artifacts that result when one or more pixels are exposed to bright light conditions. The bright light conditions cause electrons to spill over from the photodiode into the floating diffusion region, which results in an erroneous signal. For example, a reset signal sampled during a reset operation may exhibit voltage levels that are less than the desired reset level. As a result, the voltage of the pixel signal is also skewed to an undesirably small value and manifests itself as a dark spot, when it should be a bright spot. This phenomenon is generally referred to as “eclipsing,” or a “black-sun artifact.”
The circuit paths that connect the anti-eclipse circuit to other control circuits may experience failures, such as broken and/or disconnected wires/connections, that prevent the anti-eclipse circuit from operating in a desirable manner. Conventional testing methodologies are not capable of detecting such failures, and the failure is only discovered during image sensor operation. Further, conventional image sensors that are equipped with an anti-eclipse circuit do not employ any self-testing methods nor do they have a back-up circuit that can be activated in the event of a circuit failure.